This process is used when part of the mold is open. Slush
molding is an excellent method for producing hollow open-end objects.
It is an inverse of the dipping process in which the inside of the mold
is coated rather than the outside. Awide variety of products are manufactured
in this way including toys, dolls, shoes, seat covers, and automotive
parts. Open end molds are used and the excess plastisol poured off after
a gelling period. Fine details can be obtained and undercuts present few
problems. The mold cavity is usually 1-2" taller than the actual
part so that some plastisol can be trimmed after molding.

Procedure

1. The mold cavity should be coated
with a layer of mold release. We recommend MRV 1000 IPA. Please
see MRV
1000 IPA instructions.

2. The mold cavity is filled with
plastisol.

3. The mold is then heated using an
oven, or liquid bath of hot oil or molten salt. Thin walled molds are
desireable for quick heat transfer. The thickness of the coating will
depend on the temperature of the bath /oven, the time heated in the bath
/oven, and the gellation temperature of the plastisol. In an oven, the
top of the mold must be covered or a layer of gelled material will form
at the open surface.

4. After gelling a coat in the mold
the excess plastisol is emptied and the mold is allowed to drain until
the dripping stops (about 3 to 5 minutes). Plastisol that is drained from
the mold is poured through a strainer and reused. The vinyl buildup produces
a very even surface.

5. After the draining process the
mold is heated again to cure the plastisol. The cure time is usually 3
to 8 minutes.

6. The mold and plastisol can be air
or water cooled to 150°F. The heat transfer liquid must be water souluble
if water cooling. Extract the part by pulling and twisting the part. The
collapsed part has good memory and will "snap" back into place
after extraction.

Heat Transfer liquids for the
Slush Molding process

A number of heat transfer liquids
are available for using in a gel bath: plasticizers, molten salt, or any
other liquid that can reach 350° to 400°F. When using liquids
heat generally will transfer much quicker. Do NOTuse water,
water can contaminate plastisol and make it unuseable.

Mold making

Electroplated molds are used most
often in this process due to quick heat transfer. Electroforming is used
most often because of the strong, thin, highly detailed durable molds
formed in the process. Electroplating can be done over a number of substrates
including silicone. Call a professional mold maker for more information.